KR20080114722A - Apparatus and method for machining bevel gears in a pitching method with complete pitch error compensation - Google Patents

Abstract

The invention relates to apparatuses for machining bevel gears in a pitching method and method for machining the pitch of gears, wherein the production-related pitch error is compensated. The apparatus (20) comprises an interface (11, 12) and can be connected to a measurement system (10) by means of this interface (11, 12), wherein the interface is designed such that the apparatus (20) can take correction values or correction factors from the measurement system (10) in a form in order to be able to adapt master data or neutral data which was originally present in a memory (51) of the apparatus (20) on the basis of these correction values or correction factors before production of one or more bevel gears (31) is initiated on the apparatus (20). ® KIPO & WIPO 2009

Description

Apparatus and method for machining bevel gears by pitching method with full pitch error correction {APPARATUS AND METHOD FOR MACHINING BEVEL GEARS IN A PITCHING METHOD WITH COMPLETE PITCH ERROR COMPENSATION}

The present invention relates to an apparatus for machining bevel gears by an indexing method and a method for indexing machining of a gear wheel, wherein manufacturing-related indexing errors are compensated.

Fundamentally, there is a distinction between a machine tool operating in an indexing manner and a machine tool operating continuously. In the case of the indexing method, the tooth gap is machined, and then the tool is moved out of the tooth groove in a relative displacement movement, and so-called indexing movement (indexing rotation) takes place, in which the next tooth groove is machined. The gearwheel rotates with respect to the tool before it is released. The gearwheels are thus manufactured step by step. Gear cutters operating in an indexing method typically have an indexing device that rotates the workpiece by one or more indexes around the workpiece axis before the tool reengages.

In modern machines, a CNC controller is employed, which is designed so that the indexing movement can be executed at the appropriate moment.

The continuous method, sometimes called the continuous indexing method, is based on a more complex sequence of movements, in which the tool and the workpiece to be machined perform a continuous indexing movement with respect to each other. The indexing movement is caused by coordinated driving of the multi-axis drive.

The indexing method has the disadvantage that so-called indexing errors occur. These errors are caused because the temperature of the workpiece changes during gear cutting by milling the workpiece. As the temperature increases, a variation results from a preset value. Indexing errors also occur during grinding, which are not caused by heating (the abrasive oil is used in operation), but by the wear of the tool during the processing of individual tooth grooves. The abrasive disc is typically redressed before each new workpiece, so that similar wear occurs for each workpiece over the individual tooth grooves.

To this extent, indexing errors are corrected in that the sum of the indexing errors is determined and turned into a correction value. The sum of indexing errors is typically divided by the number of teeth, whereby so-called linear correction is achieved. This type of correction is unsatisfactory because all teeth may change when linear correction is made, which may result in a change of the tooth that is actually seated in the correct position.

Accordingly, the present invention is based on the object of providing an approach that enables the indexing method to be more accurate and automated in mass production of bevel gears.

This object is achieved by the device according to claim 1 and the method of claim 6.

This object is achieved in accordance with the present invention, in which the apparatus comprises a workpiece spindle for receiving the bevel gear, a tool spindle for receiving the milling tool, and a plurality of drives for machining the bevel gear in a single part method. Used. In this single indexing method, one tooth groove of the gearwheel is machined, then a relative movement is performed between the tool and the workpiece to remove the tool from the tooth groove, and the bevel gear performs a partial rotation and the milling tool It is fed in to machine additional tooth grooves. In accordance with the present invention, the drives are operable through the controller in such a way that relative movement and partial rotation occur such that the indexing error established in the previous workpiece sample produced in the device is corrected for the bevel gear to be manufactured in the current device.

The object of the present invention is achieved according to the present invention, in which a special six-axis device is used to machine the bevel gear, which has a workpiece spindle for receiving the bevel gear and a tool spindle for receiving the tool. And drives for machining the bevel gear using a tool. The device performs the following steps, in which case both teeth of the tooth grooves are manufactured simultaneously and each step is as follows:

Predefining master data or neutral data describing the shape of the bevel gear to be mass produced and the kinematics of the required machine tool; and

Based on the master data or the neutral data, a) machining a single tooth groove of the workpiece sample using a tool by performing a machining movement and b) tool and workpiece sample to remove the tool from the tooth groove. Performing relative movement between and c) performing indexing rotation to move the workpiece sample to a different angular position and d) adding the workpiece sample using the tool by repeating steps a) to c) above. Machining the tooth grooves, wherein steps a) to c) execute machining steps, repeated until all tooth grooves of the workpiece sample have been manufactured; and,

Identifying indexing errors (eg in a gear cutting measuring center) of all teeth of the workpiece sample; and

Determining appropriate indexing error correction per tooth; and,

Delivering or providing correction values (offset to indexing angle and / or plunging height of the tool); and

Adopting the machine data of the 6-axis device based on the correction values as a preparation for mass production of a series of bevel gears with an indexing error corrected; and,

Perform the above steps a) to d) and repeat steps a) to d) until all tooth grooves of the bevel gears with corrected indexing errors have been manufactured to use the adopted machine data for the bevels with corrected indexing errors. Manufacturing the gears.

According to the present invention, the control data or machine data is adapted to compensate for indexing error correction in such a way that the plurality of machining motions and indexing rotations are changed with respect to the original set point set during the manufacture of the workpiece sample defined by the master or neutral data. It is changed by confirmation.

In other words, the indexing error is corrected over at least two of the six axes or over all axes. Thereby at least the rotation is changed by adopting a partial rotation and the height of the tooth grooves is changed by adopting a machining movement and a tooth to tooth profile. This adoption is not a linear adoption, and individual adoptions take place per tooth or per tooth groove, respectively, in accordance with the present invention.

That is, each tooth or each tooth groove of the bevel gear to be manufactured in large quantities in accordance with the present invention is individually corrected so that each tooth or each tooth groove is seated in the "correct" position. Refer to one of the z teeth of the bevel gear. This one tooth is used as a quasi-reference tooth for correction of indexing error.

The invention relates in particular to dry milling bevel gears in a single indexing completion method. The present invention is particularly suitable for dry milling, since indexing errors become more apparent in dry milling. This is because, among other things, the temperature increases more strongly during milling than in the case of wet milling and the device cuts deeper than desired. As the material gets hotter, the tooth grooves typically also get larger. Depending on the method of manufacture, the temperature of the workpiece initially moves from room temperature to a temperature between approximately 40 ° and 50 ° at the end of the machining.

The method is also suitable for correction of indexing errors in the polishing of gear wheels. While being polished, the polishing disc is dressed before machining the part. During the polishing process, the abrasive disc is worn in its height and width directions so that the tooth grooves become shallower and narrower. The abrasive disc is redressed before machining the next part. The correction method can also be applied in this case.

After determining the indexing error for the workpiece sample, how the indexing angle (τ; indexing rotation) and / or plunging height (machining movement) is such that deep or too shallow cutting can be corrected for mass production as described. It is determined by the computer if it should be changed.

Other advantageous embodiments can be inferred from the dependent claims.

Exemplary embodiments of the invention are described in more detail with reference to the following figures.

Figure 1 shows a bevel gear milling machine according to the invention with six axes.

2 is a schematic block diagram of an apparatus according to the present invention.

3 is a schematic diagram showing the identification of the bevel gear pinion and the indexing error according to the present invention.

4A is a schematic diagram showing the cumulative indexing error of the tooth versus tooth tooth with respect to the left (convex) teeth.

4B is a schematic diagram showing the cumulative indexing error of the tooth versus tooth tooth with respect to the right (concave) teeth.

4C is a schematic diagram showing a cumulative indexing error of tooth grooves.

Fig. 5A is a schematic diagram showing the cumulative indexing error of the tooth versus tooth on the left (convex) teeth after correction according to the present invention.

Fig. 5B is a schematic diagram showing the cumulative indexing error of the tooth versus tooth on the right (concave) tooth surfaces after correction in accordance with the present invention.

5C is a schematic diagram showing the cumulative indexing error of post-correction post grooves in accordance with the present invention.

6A to 6C are detailed views showing the correction according to the present invention.

Terms used in related publications and patents are used in connection with this description. However, it should be noted that the use of these terms is to aid understanding. The protection scope of the spirit and claims according to the present invention is not limited to the interpretation by the selection of specific terms. The invention may be transferred to other terminology systems and / or fields without further action. The terms thus apply to other fields.

A first device 20 according to the invention is shown in FIG. This device 20 according to the invention may correspond, in whole or in part, to a CNC machine for producing spiral bevel gears already described, for example, in German application DE 19646189C2. The machine has a drive motor 41 for rotating the front cutter head 24 around its axis of rotation 17. The motor 41 and the front cutter head 24 are located on the first sliding portion 44, which are laterally guided to the machine tool housing 3 and movable in the height direction (parallel to the Z axis). The machine tool housing 36 is in turn movable horizontally (parallel to the X direction) in the machine tool bed 47 with a second sliding portion 45 further positioned on the machine tool bed. This second sliding portion 45 is mounted to the workpiece carrier 48 and is rotatable around a vertical axis C having a workpiece 31 and a workpiece spindle 49 which can rotate about a horizontal axis 32. 48) transport. The second slide 45 may move horizontally (parallel to the Y axis), but may move perpendicular to the X axis of the machine tool housing 36 and perpendicular to the Z axis of the first slide 44. . The parts of this machine tool thus form the mechanical requirements for manufacturing bevel gears by a rolling process in a single indexing method using indexing correction according to the invention. The decisive difference of the device according to the invention in comparison with a typical device is to have a modified control means of the CNC controller, which is housed in the switch cabinet 33. According to the invention, the control means has a controller for loading new control data after the production of at least one workpiece sample, which is used for mass production of bevel gears with indexing errors corrected.

According to the present invention, the tooth groove of the bevel gear is machined after infeed movement. This procedure is called a machining procedure and the corresponding movement is called a machining movement. And relative movement occurs between the tool and the workpiece to remove the tool from the tooth groove. The relative movement may be a tilting movement or a movement in which translational movement and tilt movement are combined.

The tool is removed from the tooth grooves by relative movement without colliding with directly fabricated tooth flanks of adjacent teeth. According to the invention, the indexing rotation is now carried out about the axis of rotation of the workpiece and the tool is fed back. This indexing rotation is slightly altered with respect to the corresponding partial rotation that was performed on the workpiece sample to compensate for indexing errors.

In the apparatus 20 according to the invention with a CNC controller, indexing error correction is performed "electronically", ie by appropriately adopting individual movement sequences.

The controller according to the invention can be programmed in such a way that the changed control data is loaded before starting the actual mass production and adopts the machine data, i.e. the data to build the movement of the individual axes.

Particularly preferred is an embodiment in which the CNC controller has a special software module (eg software module 11 in FIG. 1), which is modified from the measuring machine tool 10 as indicated by the arrow 12 in FIG. 1. Allow control data to be accepted.

A corresponding block diagram of the apparatus 20 according to the invention is shown in FIG. The device 20 has six drives (X, Y, Z, B, C, A1), which are shown as functional blocks in FIG. Each of these drives is controlled by a CNC controller 40. In the example shown, the connection of the drives with the CNC controller 40 is shown by a double arrow, indicating that the drives can provide feedback to the controller 40. Rotational drives B, C1 and A1 can provide feedback with respect to torque, for example an angular encoder can be used to transmit the angular position to the controller 40. For example, the drive (X, Y, Z) can send information to the controller via a distance or position encoder. In the illustrated embodiment, the controller 40 is connected to the software module 42. This software module 42 provides access to the data memory 51, for example, and can provide a data format convertible by the controller 40.

According to the invention, for example, software module 42 may be designed in a manner that allows for the manufacture of one or more workpiece samples based on certain control data 45. This control data 45 may be predetermined from a computer or other system, for example via the connection 46. The control data 45 is stored in the memory 51 and can be used directly to control the device 20 when the device 20 is designed for the purpose of directly converting this control data 45. For this purpose, the data is retrieved from the memory 51 via the connection marked 47. However, it is conceivable that other forms of data may be transferred to the memory 51 instead of the control data, depending on the embodiment. For example, software module 42 may be used in a manner that accepts data through connection 44 and converts it into control data 48 or control information prior to performing a move for production.

As already noted in connection with Fig. 1, an embodiment is preferred in which the CNC controller 40 has a special software module (e.g., a software module 11), which is indicated by an arrow 12 in Fig. 2. As is possible, data can be received from the measuring machine tool 10. The software module 11 confirms the changed control data 48 'for mass production.

Alternatively, the controller 40 receives or loads modified control data 45 'from the measuring machine tool or from a computer connected to the measuring machine tool (for example, the computer 50 shown in FIG. 2). The changed control data 45 'can overwrite the control data 45 of the memory 51. This alternative is shown in dashed lines in FIG. In this case, the changed control data 45 'is used for mass production.

3 is a detailed view of the front portion of the bevel gear pinion K1. Confirmation of indexing error according to the present invention is explained based on this figure. According to the DIN standard, it starts with the number 7 of the last tooth. All indexing errors are measured in comparison with this tooth 7 (reference tooth). The indexing angle from the right side (concave) of the toothed part 7 to the right side (concave) of the toothed part 1 is RF ₁ , and the left side (convex) of the toothed part 1 from the left side (convex) of the toothed part 7. The indexing angle up to) is LF ₁ . The indexing angles of the other teeth are similarly always measured with respect to the seventh tooth. Each of the lines S1 and S2 represents an ideal case or a set value case, but there is no deviation in this case. Angle shifts upward or downward are indicated by "-" and "+" symbols. Arrow U indicates the direction of rotation.

4A shows the accumulated indexing error of the tooth versus tooth tooth with respect to the left (convex) tooth surface. This example is a case where the bevel gear pinion has a tooth count (z) = 12. The teeth are numbered in Fig. 4A. The 12th and last teeth are again reference teeth. The cumulative indexing deviation is indicated by line L1. All teeth 1 to 11 have indexing errors with respect to the left tooth surface.

FIG. 4B shows the cumulative indexing error of the tooth versus tooth relative to the right (concave) tooth surface of the bevel gear pinion as shown in FIG. 4A. The teeth are also numbered in FIG. 4B. The cumulative indexing deviation is represented by line R1. All teeth 1 to 7 have an indexing error with respect to the right tooth surface in the example shown.

4C shows the cumulative indexing error of the tooth grooves of the bevel gear pinion according to FIGS. 4A and 4B. The width of the tooth grooves is shown by the length of the I-shaped bar and the position of the tooth grooves is represented by the up and down displacement of the I-shaped bar. By definition, the 12th groove has the correct width and position of the groove. All other tooth grooves show deviations.

If those shown in Figs. 4A-4C are representations of a workpiece sample, the bevel gear pinions are mass produced as shown in Figs. 5A-5C. Before this mass production begins, indexing errors are corrected as described earlier.

FIG. 5A shows the cumulative tooth versus tooth indexing error for the left (convex) tooth surface of a mass produced bevel gear pinion. The cumulative indexing deviation is indicated by line L1 '. Only the teeth 1 to 8 still have visible indexing errors with respect to the left tooth surface.

FIG. 5B shows cumulative tooth versus tooth indexing error for the right (concave) tooth surface of a mass produced bevel gear pinion. The cumulative indexing deviation is represented by line R1 '. The indexing deviation of all teeth is very small in this tooth plane.

5C shows the cumulative indexing error of the tooth grooves of the mass produced bevel gear pinion. All other tooth grooves still show slight deviations in position. The width of the grooves is almost ideal.

Of course, the present invention can also be used to manufacture individual bevel gears.

The mathematical approach used in one preferred embodiment of the present invention to detect indexing errors is illustrated in Figures 6A-6C. Start with the chi grooves. However, the same approach can also be performed using teeth. In Fig. 6A, the left tooth groove of the reference tooth portion is line A _last and the left tooth groove of the other tooth portion (n-th tooth portion) is line A _n . You can see that the nth tooth groove is allocated too high and the groove width is rather small. The intermediate step of the method is shown in Figure 6b. The tooth groove (A _n ) is shifted to the left and marked as A _n ', which is the corrected or modified tooth groove. This movement of the tooth groove is performed in such a way that the center line of the two tooth grooves coincide. In this figure, the direction of the plunging height U (B = 0, X) in the radial direction can be seen. The radial distance X of the teeth to one another can also be ascertained.

The last groove is shown by the line A _last and corresponds to the set point position of the nth groove. The deviation of the two tooth surfaces is represented by fu in each case. The deviation value corresponds to the deviation shown in the measurement log of FIGS. 4A and 4B.

The nth groove is moved through height change (X; plunging movement) and workpiece rotation (B; indexing movement) in such a way that the deviation (fu; see FIGS. 6A and 6B) becomes zero. This is done for each groove.

As explained, indexing errors are identified at the gear cutting measuring center 10, which may be connected at least temporarily to the device 20 to form a closed loop type. The identification of indexing errors is performed separately for all teeth of the workpiece sample and the indexing errors are thus measured for neutral or master data.

The identification according to the invention of the appropriate indexing error correction is based on the sum of indexing errors per tooth for tooth teeth (concave and convex) and always relates to the last tooth top as described above. The deviation is set to zero at the last tooth. Device or control data is employed in a closed loop. To this end, correction values (offsets) or correction factors are transmitted online to the device 20 where they are merged or applied to machine tools or control data. This means that the gear cutting measuring center 10 only transmits correction values (offsets) or correction factors.

According to the invention, the measuring center 10 is designed on the one hand in such a way that it is possible to carry out a novel method for identifying indexing errors and for determining correction values (offsets) or correction factors. The measuring center 10 must then be designed in such a way that these corrections (offsets) or correction factors can be transmitted to the device 20 in a suitable form via the interface or connection 12.

The teeth are preferably unchanged and the position and height of the grooves are changed. This is preferably done by computer superposition of the triangles as shown in Figs. 6A and 6C. Indexing error correction is performed per tooth groove so that each tooth groove is positioned as required for the last tooth groove.

In a preferred embodiment, the tolerance can be preset and only those teeth or tooth grooves that deviate from this tolerance are individually corrected.

Claims (11)

Workpiece spindle 21 for receiving bevel gear 31, tool spindle 42 for receiving tool 24, and a plurality of drives (X, Y) for machining bevel gear 31 in a single indexing method. In the device 20, which comprises Z, B, C, A1, the tooth grooves of the bevel gear 31 are machined in a single indexing method. The device 20 has interfaces 11, 12 and can be connected to the measurement system 10 via the interfaces 11, 12, which interface allows the device 20 to bevel one or more on the device 20. Measurement system 10 in a form that allows for the adoption of neutral data or master data originally present in memory 51 of device 20 on the basis of correction values or correction factors before the manufacture of gear 31 is commenced. Device 20, characterized in that it is designed in such a way that it is possible to receive correction values or correction factors from the apparatus. Apparatus (20) according to claim 1, characterized in that the tool (24) is a milling tool, preferably a dry milling tool. Apparatus (20) according to claim 1, characterized in that the tool (24) is an abrasive tool, preferably an abrasive disk which can be dressed. Apparatus (20) according to claim 1 or 2, characterized in that a closed loop can be built with the measuring system (10). 5. Apparatus (20) according to any one of the preceding claims, characterized in that it is designed to automatically execute at least some of the sequences to produce a large number of bevel gears (31). Machining the bevel gear 31 using the workpiece spindle 21 to receive the bevel gear 31, the tool spindle 42 to accommodate the tool 24, and the tool 24 in a single indexing method. A method of manufacturing a bevel gear 31 having an indexing error corrected by using a device 20 having a plurality of drives (X, Y, Z, B, C, A1) for Predefining master data or neutral data describing the shape of the bevel gear 31 to be mass-produced and the required motion transfer of the machine tool; and Based on the master data or neutral data, a) performing a machining movement to machine one tooth groove of the workpiece sample using the tool 24 and b) removing the tool 24 from the tooth groove. To perform a relative movement between the tool 24 and the workpiece sample, and c) to perform an indexing rotation to move the workpiece sample to a different angular position; and d) to repeat the steps a) to c). Machining the additional tooth grooves of the workpiece sample using the tool 24, wherein steps a) to c) are repeated, until the machining of all tooth grooves of the workpiece sample is completed; , Transferring the workpiece sample to the measurement system 10; and Identifying indexing errors of all teeth of the workpiece sample; and Determining a correction value or correction factors per tooth or per tooth groove; and Passing or accepting a correction value or correction factors; and Adopting the machine data or the neutral data of the apparatus 20 on the basis of a correction value or correction factors as a preparation for manufacturing the at least one bevel gear 31 whose indexing error is corrected; and Performing steps a) to d) to produce at least one bevel gear with an indexing error corrected using the adopted machine data, wherein all steps of the bevel gear 31 with indexing error are corrected; Repeating steps a) to d) until the grooves are manufactured. 8. A bevel gear (31) having a corrected indexing error according to claim 7, characterized in that the teeth or tooth grooves of the workpiece sample are used as a criterion for determining a correction value or correction factor per tooth or per tooth groove. Way. 8. A method according to claim 6 or 7, wherein each tooth or each tooth groove undergoes individual correction. 8. Method according to claim 6 or 7, wherein the tolerance is pre-defined and only the teeth or tooth grooves which deviate from the tolerance undergo individual correction. 10. Method according to any one of the claims 6 to 9, characterized in that it is a bevel gear milling method, preferably a dry milling method. 10. Method according to any one of the claims 6 to 9, characterized in that it is a polishing method, preferably a method of using a polishing disk which can be dressed.

Images